Mason is a Perl-based web site development and delivery
system. Mason allows web pages and sites to be constructed from
shared, reusable building blocks called components. Components contain
a mix of Perl and HTML, and can call each other and pass values back
and forth like subroutines. Components increase modularity and
eliminate repetitive work: common design elements (headers, footers,
menus, logos) can be extracted into their own components where they
need be changed only once to affect the whole site.